Slow releasing electromagnetic apparatus



A March 19, 1935. s. M. LUCAS 1,994,723

SLOW RELEASING ELECTROMAGNETIC APPARATUS Filed Dec. 30. 1933 2 A -35 A I iiji; a i:;c E v? I 4 1* .Lf ia F'Lg. Z

INVENTOR Samuel M Lucas BY HIS ATTORNEY Patented Mar. 19, 1935 I UNITED STATES- PATENT OFFICE SLOW BELEASING ELECI'BOHAGNETIC APPARATUS Application December 30, 1933, Serial No. "4,802

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My invention relates to electromagnetic apparatus, and has for an object the provision of novel and improved means for prolonging the energization of an electrical device such as an electro-magnet and thereby, in the case of a magnet, delaying the release of the armature of the magnet for a considerable period of time after the winding of the magnet becomes deenergized.

The usual means for delaying the release of a magnet involves a short-circuited winding, usually a copper tube, on the core of the magnet, and in the case of a railway signaling relay provided with this expedient the release time may be made as high as 1.5 seconds. In some cases greater retardation is necessary, and when so, an additional increase in retardation is obtained by connecting a rectifier in the proper direction across the terminals of the relay winding. By this means a retardation of about 1.8 seconds may be obtained. One object of my invention is the provision of means for retarding the release of an electro-magnet for an even greater period of time. Instead of depending solely upon the energy stored in the magnetic circuit of the electro-magnet for retardation, additional energy may be stored in an auxiliary and independent electromagnetic circuit, and by this means I am able to obtain a retardation which is limited only by the economic value of the time required for the magnet to release.

I will describe two forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is 9. diagrammatic view showing one form of apparatus embodying my invention. Fig. 2 is a view showing a modification of the apparatus shown in Fig. 1 and also embodying my invention.

Similar reference characters refer to similar parts in each of the views.

Referring firstto Fig. 1 of the drawing, the reference character C designates an electromagnetic device which, as here shown, is a relay comprising the usual magnetic core 6, operating winding 7, and armature 8. This relay is at times energized by a battery B through a control contact 4 and branches Rw and Rz of a full-wave rectifier R consisting of four paths Rw, Rx, By and R2 each of which offers low resistance to, and may conduct current freely in the direction shown by the arrows but which offer high resistance to current flowing in the direction opposite to the arrows. Connected across the input terminals 9 and 10 of the rectifier R is an inductor A, comprising a magnetizable core 2 provided with a winding 3.

When the contact 4 is closed, current flows through the inductor winding 3 in' the direction indicated by the heavy arrows, and current also flows through the rectifier R and the winding 7 of relay C in the direction indicated by the heavy arrows. It follows that the armature 8 of relay C will be closed, that energy will be stored in the magnetic circuit of this relay, and that energy will also be stored in the magnetic circuit of the inductor A. If now the contact 4 is opened, the supply of current from battery B to the inductor A and to relay C will be discontinued. The

collapse of the magnetic flux in the inductor will produce a transient electromotive force in the winding of the inductor A of such polarity as to continue the flow of current in the winding of the inductor, and likewise the collapse of the magnetic flux in the relay C will produce a transient electromotive force in the winding of the relay of such polarity as to tend to continue the flow of the current in the relay winding. The resulting flow of current in the various parts of the circuit due to transient electromotive forces can best be explained by means of the principle of superposition. Loosely stated this principle of superposition is: When two or more electromotive forces exist in a network, each electromotive force acts independently to establish voltages and currents in the various parts of the network and the actual (or total) currents or voltages at any given point in the network are the algebraic sums of the currents or voltages established at that point due to the several independent electromotive forces.

Now consider the current which will flow due to each of the two transient electromotive forces aforementioned. The transient electromotive force from the relay C, if acting independently, would cause a current to flow in the direction of the arrows from winding 7 to terminal 12 of rectifier R, thence through the rectifier by two paths (one consisting of R1: and B10 in series and the other path consisting of R2 and Ry in series) to terminal 11 and back to the winding. Since the branches Rw, Rx, R11 and R2 of the rectifier are all of approximately the same resistance, the potential of terminal 10 to terminal 9 is practically zero, and hence the independent transient current due to the transient electromotive force 'in relay C does not flow to the winding of ininductor A, if acting independently, would cause a current to how in the direction oi the dotted arrows from the winding to teal of net work R, through branch Ry to terminal 11, thence through winding 7 of relay C to terminal 12 of rectifier R, through branch Re to terminal 9, and then return to the winding 3 of inductor A. And now when the two independent transient electromotive forces act simultaneously and the currents are added in accordance with the principle or super-position, it is found that the two transient electromotive forces have increased the transient current in the winding of relay C to a value higher than that which would exist if only the transient electromotive force of relay C were acting alone.

The operation of apparatus embodying my invention depends on the fact that when contact d-is openedthe multipleconnection of the inductor A and the relay C is instantly switched to the series connection above described by means of the four elements of the rectifier R. By properly choosing the size oi the inductor A, the rate of decay of the energy in this inductor may be made such as to produce any desired period of release for the relay C. a 1

One advantage of apparatus embodying invention is that thepick-up time of the relay C is not affected, so that when contact 4 is closed, the-armature of relay 0 will close as quickly as if the inductor A were not provided. The reason for this is that there is no reaction between the inductor and the relay during the growth of current in the two magnetic structures.

Another advantage of my invention is that the slow-release characteristic of the relay may be modified by varying the proportion of the inductor winding 3 which is included in the circuit. As shown in the drawing, this may be done by means of a contact member 5. .When contact 5-6 is closed, relay C will have a relatively long retardation period, because all of the winding 3 will be included in the relay circuit. When contact 5-5 is closed, however, a portion of winding 3 will be excluded from the circuit, and the retardation time oi relay C will be decreased.

Referring now to Fig. 2, the battery B is connected across a portion 3 of the winding of inductor A through the contact 4, and the winding 6 of relay C is also connected across the portion 3 of the inductor winding through a half-wave rectifier Ra poled to freely conduct the current which is supplied to relay C by battery B when contact 4 is closed. The remaining portion 3' of the winding of inductor A is also connected across winding 6 of relay C through-another rectifier Rb, which is so poled as to oppose the flow of current from battery B.

When contact 4 is closed, current from battery B flows through the lower portion 3 of the winding of inductor A and through the winding of.

relay 6 in the directions indicated by the solid arrows, but this current cannot flow through the upper portion 3 of the inductor winding, be-

to create transient currents which flow domiwardly in the reactor winding sections 3 and 3 Transient current cannot flow from winding section 3 through the relay C because it is blocked by rectifier Ra, but transient current can flow from the upper winding section 3 through the relay C and rectifier Rb in the direction indicated by the dotted arrows, and this transient current from the inductor adds to the transient current in the relay winding which exists due to the collapse of the magnetic field of the relay, and hence the transient current from the inductor increases the current which flows through the relay after the opening of contact 4, and thereby delays the release of relay C.

Although I have hereinshown and described only two forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without' departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a source of direct current, an inductor, means for connecting said inductor with and disconnecting it irom'said source, a

rectifier having its input terminals connected across at least a portion of said inductor, and an electromagnetic device having a winding con nected with the output terminals of said rectifier, whereby when said inductor becomes disconnected from said source the energy which is stored in the inductor discharges into said electromagnetic device to prolong the energization of the device and thereby delay its release.

2. In combination, a source of direct current, an electrical energy storing element, means for connecting said element with and disconnecting it from said source, a rectifier having its input terminals connected with said element, and an electromagnetic device having a winding connected with the output terminals of said rectifler,-whereby when said element is connected with said source both the element and said device are energized from the source and when the element becomes disconnected from the source the energy which is stored in the element discharges into said device to prolong the energization of the device and thereby delay its release.

3. In combination, vice, an inductor, a source of direct current, means for at times connecting said source with and at other times disconnecting it from said device and said inductor, and means operating when said source becomes disconnected from said device and said inductor to supply a transient current from said inductor to said device which flows through said device in the same direction as the current from said source.

4. In combination, an electromagnetic device, an inductor, a source of direct current, means for at times connecting said source with and at other times disconnecting it from said device and a portion 01' the winding of said inductor in multiple, a rectifier interposed between said inductor winding and said device and poled to conduct the current supplied to the device when said source is connected therewith, and means for connecting another portion of said inductor winding with said device through a rectifier which is poled to conduct the transient current which flows from said second portion of the inductor to the device when the source becomes disconnected.

5. In combination, an element capable oi storing electrical energy, an electromagnetic an electromagnetic dedevice, a source of current for at times supplying energy to said element and said device, and means operating when said source is disconnected to supply from said element to said device a transient current of the same polarity as that which is supplied by said source.

6. In combination, a source of direct current, an electrical energy storing element, means for connecting said element with and disconnecting it from said source, and an electrical device connected with said element through a rectifier.

'7. In combination, an inductor, meansior at times supplying direct cun-ent to at least a portion or the winding of said inductor, and an electrical load connected with at least a portion of the winding of said inductor through a rectifier.

8. In combination, a source of direct current, an inductor, means for connecting said inductor with and disconnecting it from said source, a rectifier having its input terminals connected across at least a portion of said inductor, a circuit connected with the output terminals of said rectifier whereby when said inductor becomes disconnected from said source the energy which is stored in said inductor discharges into said circuit to prolong the flow 01' current therein.

SAMUEL M. LUCAS. 

